Recently, the availability of cellular telephone communication service has increased dramatically. All major metropolitan areas, and many less populated areas, are served by at least one cellular telephone company. The development of this cellular network has resulted in providing a widespread capability to communicate with a mobile telephone subscriber by the use of an RF cellular telephone channel and the existing public switched telephone network, almost anywhere in the country. As cellular telephone systems and equipment have proliferated, there has developed an increased demand for the transmission of not only voice information, but also data. Unfortunately, the transmission of data over a cellular telephone link presents additional problems not encountered with the transmission of simple analog voice information.
In particular, while the introduction of noise into voice communication may create some problems of intelligibility, in general, unless there is a complete loss of signal, the voice message will still be transmitted and recognized. On the other hand, when transmitting data in a digital form, any noise encountered on the communications channel will most likely corrupt the data being transmitted, thereby requiring the same data to be retransmitted. Similarly, a break in transmission while transmitting data, as is often the case in cellular transmissions, requires retransmission of all of the data. Retransmission of data results in a lower throughput bandwidth due to the extended time necessary to transmit data. In addition, since the cellular network is more expensive to use due to its associated higher tariffs (compared to comparable land lines), such retransmission can increase operating costs substantially.
While it has been known to interface common data terminal equipment and modems to a cellular telephone transceiver, such attempts have not been optimized for use in a cellular RF environment, and thus are large, expensive and inefficient.
Accordingly, it has been determined that the need exists for an improved apparatus for the transmission of data over an RF channel which will provide increased reliability of data transmission as well as a reduction of operating costs, thereby improving upon the above-noted limitations of the prior art.